Epichlorohydrin rubbers are noted for their excellent oil resistance, combustion resistance and heat resistance. The most typical of the epichlorohydrin rubbers are the homopolymers of epichlorohydrin (CHR), copolymers of epichlorohydrin and ethylene oxide (CHC), and binary and ternary copolymers formed by modifying CHR and CHC with allylglycidyl ether. As the vulcanizing agent for epichlorohydrin rubbers, 2-mercaptoimidazoline, diethylthiourea, dibutylthiourea, hexamethylenediamine carbamate, etc. are known, but there is a known defect in the vulcanization of epichlorohydrin rubber using those known vulcanizing agents, in that the mold is heavily stained. In order to avoid the mold staining, an acid acceptor such as red lead, zinc flower or magnesium oxide must be concurrently used. However, use of such an acid acceptor, which is injurious to human health, is undesirable because it is eluted during use of the final rubber product. Therefore, the rubber product cannot be used in the fields of medicines and foods, for example, as bottles and stoppers. Particularly when red lead is used, the epichlorohydrin rubber, after the vulcanization, exhibits excellent physical properties, but the toxicity of the lead compound presents a serious problem during the fabrication of said rubber.
We have found that a specific group of amino acids possess excellent vulcanizing effect on epichlorohydrin rubber, and furthermore that quite unexpectedly the amino acid causes no mold staining even when used without an acid acceptor. The present invention has been completed on the basis of these findings.